A recent aerial survey exposed latent structures—palaces, roadways, houses—that are altering long-held notions of the size and density of the Mesoamerican civilization.

“Frankly, it’s turning our discipline on its head,” Thomas Garrison, assistant professor of anthropology at Ithaca College, said in a statement.

Garrison, a National Geographic Explorer who specializes in digital technology for archaeological research, led the 2016 project. Using LiDAR (light detection and ranging), a group of scientists were able to map the “steamy” jungles of northern Guatemala from the sky.

An airplane-mounted device sends a constant pulse of laser light across the terrain below; precise measurements of how long it takes the emitted beams to bounce off surfaces are translated into topographic data.

The laser, able to pierce through the smallest gaps in vegetation, can record the ground “with remarkable accuracy,” according to Ithaca College. After digitally filtering out trees, researchers can get a better view of what lies beneath.

A comparison of LiDAR data showing the ancient Maya site of El Zotz covered in trees (left), and with the trees digitally removed (via Ithaca College)

This is especially important in tangled forests like those in lowland Guatemala, where other methods of aerial survey can’t penetrate thick undergrowth.

“In that kind of environment where you can’t see [a few feet in front of yourself], it’s very hard to piece that all together,” Garrison said. “You have this idea that there’s some little stuff on the hills, but the LiDAR lets you see it in its totality.”

A survey of 2,100-square kilometers—covering major Maya sites like Tikal and El Zotz—revealed more than 60,000 previously unknown structures, including unknown pyramids, palace structures, terraced fields, roadways, defensive walls and towers, and houses.

What’s being hailed as a “major breakthrough” highlights ancient population centers that are more extensive than once believed; population estimates have been expanded from a few million to 10 or 20 million.

“Everyone is seeing larger, denser sites. Everyone,” Garrison said. “There’s a spectrum to it, for sure, but that’s a universal: Everyone has missed settlement in their [previous] mapping.”

The findings—and the LiDAR technology behind them—are the focus of a new National Geographic documentary, “Lost Treasures of the Maya Snake King.” Set to premiere Tuesday at 9 p.m. EST, the broadcast follows a NatGeo explorer through the jungle as he searches for a laser-detected pyramid.